Pyrimidine derivatives as selective inhibitors of cox-2

ABSTRACT

The invention thus provides the compounds of formula (I) 
                         
and pharmaceutically acceptable salts thereof, in which:
     R 1  and R 2  are independently selected from the group consisting of H, C 1-6 alkyl, C 2-6 alkenyl, C 3-6 alkynyl, C 3-10 cycloalkylC 0-6 alkyl and C 4-12 bridged cycloalkyl;   R 3  is selected from the group consisting of C 1-6 alkyl, NH 2  and R 5 CONH;   R 4  is selected from the group consisting of CH 2 F, CHF 2 , CF 3 CH 2 , CF 3 CHF and CF 3 CF 2 ; and   R 5  is selected from the group consisting of H, C 1-6 alkyl, C 1-6 alkoxy, C 1-6 alkylOC 1-6 alkyl, phenyl, HO 2 CC 1-6 alkyl, C 1-6 alkylOCOC 1-6 alkyl, C 1-6 alkylOCO, H 2 NC 1-6 alkyl, C 1-6 alkylOCONHC 1-6 alkyl and C 1-6 alkylCONHC 1-6 alkyl.   
     Compounds of formula (I) are potent and selective inhibitors of COX-2 and are of use in the treatment of the pain, fever, inflammation of a variety of conditions and diseases.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a 371 Application of PCT/GB02/02414, filed 23 May2002, which claims priority to GB Application Serial No. 0112810.7,filed 25 May 2001.

This invention relates to pyrimidine derivatives, to processes for theirpreparation, to pharmaceutical compositions containing them and to theiruse in medicine.

The enzyme cyclooxygenase (COX) has recently been discovered to exist intwo isoforms, COX-1 and COX-2. COX-1 corresponds to the originallyidentified constitutive enzyme while COX-2 is rapidly and readilyinducible by a number of agents including mitogens, endotoxin, hormones,cytokines and growth factors. Prostaglandins generated by the action ofCOX have both physiological and pathological roles. It is generallybelieved that COX-1 is largely responsible for the importantphysiological functions such as maintenance of gastrointestinalintegrity and renal blood flow. In contrast the inducible form, COX-2,is believed to be largely responsible for the pathological effects ofprostaglandins where rapid induction of the enzyme occurs in response tosuch agents as inflammatory agents, hormones, growth factors andcytokines. A selective inhibitor of COX-2 would therefore haveanti-inflammatory, anti-pyretic and analgesic properties, without thepotential side effects associated with inhibition of COX-1. We have nowfound a novel group of compounds which are both potent and selectiveinhibitors of COX-2.

The invention thus provides the compounds of formula (I)

and pharmaceutically acceptable salts thereof, in which:

-   R¹ and R² are independently selected from the group consisting of H,    C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₆alkynyl, C₃₋₁₀cycloalkylC₀₋₆alkyl and    C₄₋₁₂bridged cycloalkyl;-   R³ is selected from the group consisting of C₁₋₆alkyl, NH₂ and    R⁵CONH;-   R⁴ is selected from the group consisting of CH₂F, CHF₂, CF₃CH₂,    CF₃CHF and CF₃CF₂; and-   R⁵ is selected from the group consisting of H, C₁₋₆alkyl,    C₁₋₆alkoxy, C₁₋₆alkylOC₁₋₆alkyl, phenyl, HO₂CC₁₋₆alkyl,    C₁₋₆alkylOCOC₁₋₆alkyl, C₁₋₆alkylOCO, H₂NC₁₋₆alkyl,    C₁₋₆alkylOCONHC₁₋₆alkyl and C₁₋₆alkylCONHC₁₋₆alkyl.

Suitable pharmaceutically acceptable salts include acid addition saltsformed with the amine functionality NR¹R². Pharmaceutically acceptablesalts include those described by Berge, Bighley and Monkhouse, J. Pharm.Sci., 1977, 66, 1–19. Such salts may be formed from inorganic andorganic acids. Representative examples thereof include maleic, fumaric,benzoic, ascorbic, pamoic, succinic, bismethylenesalicyclic,methanesulfonic, p-toluenesulfonic, ethanedisulfonic, acetic, propionic,tartaric, salicyclic, citric, gluconic, aspartic, stearic, palmitic,itaconic, glycolic, p-aminobenzoic, glutamic, taurocholic,benzenesulfonic, hydrochloric, hydrobromic, sulfuric,cyclohexylsulfamic, phosphoric and nitric acids.

It will be appreciated that, for pharmaceutical use, the salts referredto above will be the physiologically acceptable salts, but other saltsmay find use, for example in the preparation of compounds of formula (I)and the physiologically acceptable salts thereof.

The term ‘alkyl’ as a group or part of a group means a straight orbranched chain alkyl group, for example a methyl, ethyl, n-propyl,i-propyl, n-butyl, s-butyl or t-butyl group.

It is to be understood that the present invention encompasses allisomers of the compounds of formula (I) and their pharmaceuticallyacceptable salts, including all geometric, tautomeric and optical forms,and mixtures thereof (e.g. racemic mixtures).

In one aspect of the invention R¹ is H.

In another aspect of the invention R² is C₁₋₆alkyl, such as straightchain C₁₋₆alkyl (e.g. n-propyl, n-butyl or n-pentyl).

In another aspect of the invention R² is a branched chain C₃₋₆alkyl,such as s-butyl or t-butyl (e.g. s-butyl).

In another aspect of the invention R³ is C₁₋₆alkyl, such as C₁₋₃alkyl(e.g. methyl).

In another aspect of the invention R⁴ is CH₂F or CF₂H.

In another aspect of the invention R⁵ is selected from the groupconsisting of C₁₋₆alkyl (e.g. ethyl), phenyl and aminomethyl.

It is to be understood that the invention covers all combinations ofparticular aspects of the invention as described hereinabove.

In another aspect the invention provides the following compounds:

-   N-butyl-4-(fluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine;-   N-butyl-4-(difluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine;    and pharmaceutically acceptable salts thereof.

Since the compounds of the present invention, in particular compounds offormula (I), are intended for use in pharmaceutical compositions, itwill be understood that they are each provided in substantially pureform, for example at least 50% pure, more suitably at least 75% pure andpreferably at least 95% pure (% are on a wt/wt basis). Impurepreparations of the compound of formula (I) may be used for preparingthe more pure forms used in pharmaceutical compositions. Although thepurity of intermediate compounds of the present invention is lesscritical, it will be readily understood that the substantially pure formis preferred as for the compounds of formula (I). Preferably, wheneverpossible, the compounds of the present invention are available incrystalline form.

When some of the compounds of this invention are allowed to crystalliseor are recrysallised from organic solvents, solvent of recrystallisationmay be present in the crystalline product. This invention includeswithin its scope such solvates. Similarly, some of the compounds of thisinvention may be crystallised or recrystallised from solvents containingwater. In such cases water of hydration may be formed. This inventionincludes within its scope stoichiometric hydrates as well as compoundscontaining variable amounts of water that may be produced by processessuch as lyophilisation. In addition, different crystallisationconditions may lead to the formation of different polymorphic forms ofcrystalline products. This invention includes within its scope all thepolymorphic forms of the compounds of formula (I).

Compounds of the invention are potent and selective inhibitors of COX-2.This activity is illustrated by their ability to selectively inhibitCOX-2 over COX-1.

In view of their selective COX-2 inhibitory activity, the compounds ofthe present invention are of interest for use in human and veterinarymedicine, particularly in the treatment of the pain (both chronic andacute), fever and inflammation of a variety of conditions and diseasesmediated by selective inhibition of COX-2. Such conditions and diseasesare well known in the art and include rheumatic fever; symptomsassociated with influenza or other viral infections, such as the commoncold; lower back and neck pain; headache; toothache; sprains andstrains; myositis; sympathetically maintained pain; synovitis;arthritis, including rheumatoid arthritis; degenerative joint diseases,including osteoarthritis; gout and ankylosing spondylitis; tendinitis;bursitis; skin related conditions, such as psoriasis, eczema, burns anddermatitis; injuries, such as sports injuries and those arising fromsurgical and dental procedures.

The compounds of the invention are also useful for the treatment ofneuropathic pain. Neuropathic pain syndromes can develop followingneuronal injury and the resulting pain may persist for months or years,even after the original injury has healed. Neuronal injury may occur inthe peripheral nerves, dorsal roots, spinal cord or certain regions inthe brain. Neuropathic pain syndromes are traditionally classifiedaccording to the disease or event that precipitated them. Neuropathicpain syndromes include: diabetic neuropathy; sciatica; non-specificlower back pain; multiple sclerosis pain; fibromyalgia; HIV-relatedneuropathy; neuralgia, such as post-herpetic neuralgia and trigeminalneuralgia; and pain resulting from physical trauma, amputation, cancer,toxins or chronic inflammatory conditions. These conditions aredifficult to treat and although several drugs are known to have limitedefficacy, complete pain control is rarely achieved. The symptoms ofneuropathic pain are incredibly heterogeneous and are often described asspontaneous shooting and lancinating pain, or ongoing, burning pain. Inaddition, there is pain associated with normally non-painful sensationssuch as “pins and needles” (paraesthesias and dysesthesias), increasedsensitivity to touch (hyperesthesia), painful sensation followinginnocuous stimulation (dynamic, static or thermal allodynia), increasedsensitivity to noxious stimuli (thermal, cold, mechanical hyperalgesia),continuing pain sensation after removal of the stimulation (hyperpathia)or an absence of or deficit in selective sensory pathways (hypoalgesia).

The compounds of the invention are also useful for the treatment ofother conditions mediated by selective inhibition of COX-2.

For example, the compounds of the invention inhibit cellular andneoplastic transformation and metastatic tumour growth and hence areuseful in the treatment of certain cancerous diseases, such as coloniccancer and prostate cancer. The compounds of the invention are alsouseful in reducing the number of adenomatous colorectal polyps and thusreduce the risk of developing colon cancer. The compounds of theinvention are also useful in the treatment of cancer associated withoverexpression of HER-2/neu, in particular breast cancer.

Compounds of the invention also prevent neuronal injury by inhibitingthe generation of neuronal free radicals (and hence oxidative stress)and therefore are of use in the treatment of stroke; epilepsy; andepileptic seizures (including grand mal, petit mal, myoclonic epilepsyand partial seizures).

Compounds of the invention also inhibit prostanoid-induced smooth musclecontraction and hence are of use in the treatment of dysmenorrhoea andpremature labour.

Compounds of the invention are also useful in the treatment of liverdisease, such as inflammatory liver disease, for example chronic viralhepatitis B, chronic viral hepatitis C, alcoholic liver injury, primarybiliary cirrhosis, autoimmune hepatitis, nonalcoholic steatohepatitisand liver transplant rejection.

Compounds of the invention inhibit inflammatory processes and thereforeare of use in the treatment of asthma, allergic rhinitis and respiratorydistress syndrome; gastrointestinal conditions such as inflammatorybowel disease, Crohn's disease, gastritis, irritable bowel syndrome andulcerative colitis; and the inflammation in such diseases as vasculardisease, migraine, periarteritis nodosa, thyroiditis, aplastic anaemia,Hodgkin's disease, scierodoma, type I diabetes, myasthenia gravis,multiple sclerosis, sorcoidosis, nephrotic syndrome, Bechet's syndrome,polymyositis, gingivitis, conjunctivitis and myocardial ischemia.

Compounds of the invention are also useful in the treatment ofophthalmic diseases such as retinitis, retinopathies, uveitis and ofacute injury to the eye tissue.

Compounds of the invention are also useful for the treatment ofcognitive disorders such as dementia, particularly degenerative dementia(including senile dementia, Alzheimer's disease, Pick's disease,Huntington's chorea, Parkinson's disease and Creutzfeldt-Jakob disease),and vascular dementia (including multi-infarct dementia), as well asdementia associated with intracranial space occupying lesions, trauma,infections and related conditions (including HIV infection), metabolism,toxins, anoxia and vitamin deficiency; and mild cognitive impairmentassociated with ageing, particularly Age Associated Memory Impairment.

Compounds of the invention are also useful in the treatment of disordersameliorated by a gastroprokinetic agent. Disorders ameliorated bygastroprokinetic agents include ileus, for example post-operative ileusand ileus during sepsis; gastroesophageal reflux disease (GORD, or itssynonym GERD); gastroparesis, such as diabetic gastroparesis; and otherfunctional bowel disorders, such as non-ulcerative dyspepsia (NUD) andnon-cardiac chest pain (NCCP).

According to a further aspect of the invention, we provide a compound offormula (I) or a pharmaceutically acceptable salt thereof for use inhuman or veterinary medicine.

According to another aspect of the invention, we provide a compound offormula (I) or a pharmaceutically acceptable salt thereof for use in thetreatment of a condition which is mediated by COX-2.

According to a further aspect of the invention, we provide a method oftreating a human or animal subject suffering from a condition which ismediated by COX-2 which comprises administering to said subject aneffective amount of a compound of formula (I) or a pharmaceuticallyacceptable salt.

According to a further aspect of the invention, we provide a method oftreating a human or animal subject suffering from an inflammatorydisorder, which method comprises administering to said subject aneffective amount of a compound of formula (I) or a pharmaceuticallyacceptable salt thereof.

According to another aspect of the invention, we provide the use of acompound of formula (I) or a pharmaceutically acceptable salt thereoffor the manufacture of a therapeutic agent for the treatment of acondition which is mediated by COX-2.

According to another aspect of)the invention, we provide the use of acompound of formula (I) or a pharmaceutically acceptable salt thereoffor the manufacture of a therapeutic agent for the treatment of aninflammatory disorder.

It is to be understood that reference to treatment includes bothtreatment of established symptoms and prophylactic treatment, unlessexplicitly stated otherwise.

It will be appreciated that the compounds of the invention mayadvantageously be used in conjunction with one or more other therapeuticagents. Examples of suitable agents for adjunctive therapy include a5HT₁ agonist, such as a triptan (e.g. sumatriptan or naratriptan); anadenosine A1 agonist; an EP ligand; an NMDA modulator, such as a glycineantagonist; a sodium channel blocker (e.g. lamotrigine); a substance Pantagonist (e.g. an NK₁ antagonist); a cannabinoid; acetaminophen orphenacetin; a 5-lipoxygenase inhibitor; a leukotriene receptorantagonist; a DMARD (e.g. methotrexate); gabapentin and relatedcompounds; a tricyclic antidepressant (e.g. amitryptilline); a neuronestabilising antiepileptic drug; a mono-aminergic uptake inhibitor (e.g.venlafaxine); a matrix metalloproteinase inhibitor; a nitric oxidesynthase (NOS) inhibitor, such as an iNOS or an nNOS inhibitor; aninhibitor of the release, or action, of tumour necrosis factor α; anantibody therapy, such as a monoclonal antibody therapy; an antiviralagent, such as a nucleoside inhibitor (e.g. lamivudine) or an immunesystem modulator (e.g. interferon); an opioid analgesic; a localanaesthetic; a stimulant, including caffeine; an H₂-antagonist (e.g.ranitidine); a proton pump inhibitor (e.g. omeprazole); an antacid (e.g.aluminium or magnesium hydroxide; an antiflatulent (e.g. simethicone); adecongestant (e.g. phenylephrine, phenylpropanolamine, pseudoephedrine,oxymetazoline, epinephrine, naphazoline, xylometazoline,propylhexedrine, or levo-desoxyephedrine); an antitussive (e.g. codeine,hydrocodone, carmiphen, carbetapentane, or dextramethorphan); adiuretic; or a sedating or non-sedating antihistamine. It is to beunderstood that the present invention covers the use of a compound offormula (I) or a pharmaceutically acceptable salt thereof in combinationwith one or more other therapeutic agents.

The compounds of formula (I) and their pharmaceutically acceptable saltsare conveniently administered in the form of pharmaceuticalcompositions. Thus, in another aspect of the invention, we provide apharmaceutical composition comprising a compound of formula (I) or apharmaceutically acceptable salt thereof adapted for use in human orveterinary medicine. Such compositions may conveniently be presented foruse in conventional manner in admixture with one or more physiologicallyacceptable carriers or excipients.

The compounds of formula (I) and their pharmaceutically acceptable saltsmay be formulated for administration in any suitable manner. They may,for example, be formulated for topical administration or administrationby inhalation or, more preferably, for oral, transdermal or parenteraladministration. The pharmaceutical composition may be in a form suchthat it can effect controlled release of the compounds of formula (I)and their pharmaceutically acceptable salts.

For oral administration, the pharmaceutical composition may take theform of, for example, tablets (including sub-lingual tablets), capsules,powders, solutions, syrups or suspensions prepared by conventional meanswith acceptable excipients.

For transdermal administration, the pharmaceutical composition may begiven in the form of a transdermal patch, such as a transdermaliontophoretic patch.

For parenteral administration, the pharmaceutical composition may begiven as an injection or a continuous infusion (e.g. intravenously,intravascularly or subcutaneously). The compositions may take such formsas suspensions, solutions or emulsions in oily or aqueous vehicles andmay contain formulatory agents such as suspending, stabilising andlordispersing agents. For administration by injection these may take theform of a unit dose presentation or as a multidose presentationpreferably with an added preservative.

Alternatively for parenteral administration the active ingredient may bein powder form for reconstitution with a suitable vehicle.

The compounds of the invention may also be formulated as a depotpreparation. Such long acting formulations may be administered byimplantation (for example subcutaneously or intramuscularly) or byintramuscular injection. Thus, for example, the compounds of theinvention may be formulated with suitable polymeric or hydrophobicmaterials (for example as an emulsion in an acceptable oil) or ionexchange resins, or as sparingly soluble derivatives, for example, as asparingly soluble salt.

As stated above, the compounds of the invention may also be used incombination with other therapeutic agents. The invention thus provides,in a further aspect, a combination comprising a compound of formula (I)or a pharmaceutically acceptable salt thereof together with a furthertherapeutic agent.

The combinations referred to above may conveniently be presented for usein the form of a pharmaceutical formulation and thus pharmaceuticalformulations comprising a combination as defined above together with apharmaceutically acceptable carrier or excipient comprise a furtheraspect of the invention. The individual components of such combinationsmay be administered either sequentially or simultaneously in separate orcombined pharmaceutical formulations.

When a compound of formula (I) or a pharmaceutically acceptable saltthereof is used in combination with a second therapeutic agent activeagainst the same disease state the dose of each compound may differ fromthat when the compound is used alone. Appropriate doses will be readilyappreciated by those skilled in the art.

A proposed daily dosage of a compound of formula (I) for the treatmentof man is 0.01 mg/kg to 500 mg/kg, such as 0.05 mg/kg to 100 mg/kg, e.g.0.1 mg/kg to 50 mg/kg, which may be conveniently administered in 1 to 4doses. The precise dose employed will depend on the age and condition ofthe patient and on the route of administration. Thus, for example, adaily dose of 0.25 mg/kg to 10 mg/kg may be suitable for systemicadministration.

Compounds of formula (I) and pharmaceutically acceptable salts thereofmay be prepared by any method known in the art for the preparation ofcompounds of analogous structure.

Compounds of formula (I) and pharmaceutically acceptable salts thereofmay be prepared by a process which comprises:

reacting an amine HNR¹R² of formula (II) or a protected derivativethereof with a compound of formula (III)

and thereafter and if necessary,

interconverting a compound of formula (I) into another compound offormula (I); and/or

deprotecting a protected derivative of compound of formula (I).

The overall synthesis of a compound of formula (I) is shown in Scheme 1below in which, R¹ R² and R⁴ are as defined in formula (I) above unlessotherwise stated, R³ is C₁₋₆alkyl; MTBE is methyl t-butyl ether; andalkyl is a straight or branched chain alkyl group, for example a methyl,ethyl, n-propyl, i-propyl, n-butyl, s-butyl or t-butyl group.

Referring to Scheme 1, the treatment of compounds of formula (III) withan amine of formula (II) is conveniently carried out in a solvent, suchas nitrile (e.g. methylnitrile) and at elevated temperature (e.g. fromabout 50° C. to reflux). An excess of the amine may be used in place ofthe solvent.

Alternatively, the treatment of compounds of formula (III) with an amineof formula (II) is conveniently carried out in a solvent, such as atertiary amine (e.g. NMP), and at between ambient and elevatedtemperature (e.g. ambient temperature). Use of, for example, NMP assolvent has the advantage that after completion of the reaction thedesired compound of formula (I) may be precipitated from the reactionmixture by the addition of water, allowing for easier isolation andpurification.

Conveniently the oxidation shown in Scheme 1 is effected using amonopersulfate compound, such as potassium peroxymonosulfate (known asOxone™) and the reaction is carried out in a solvent, such as an aqueousalcohol, (e.g. aqueous methanol), and at between −78° C. and ambienttemperature.

Alternatively, the oxidation shown in Scheme 1 may be effected usinghydrogen peroxide in the presence of catalytic sodium tungstatedihydrate. The reaction may be carried out in a solvent such as aceticacid and at between ambient temperature and reflux (e.g. 50° C.).

Referring to Scheme 1, the cyclisation of diones of formula (VI) to givethe corresponding pyrimidines of formula (IV) is conveniently carriedout employing a thioronium salt such as a 2-methyl-2-thiopseudoureasulfate and under reflux.

It will be appreciated by those skilled in the art that certain of theprocedures described in Scheme 1 for the preparation of compounds offormula (I) or intermediates thereto may not be applicable to some ofthe possible substituents.

It will be further appreciated by those skilled in the art that it maybe necessary or desirable to carry out the transformations described inScheme 1 in a different order from that described, or to modify one ormore of the transformations, to provide the desired compound of formula(I).

In one variation of Scheme 1, compounds of formula (III) wherein R³ isC₁₋₆alkyl or NH₂ may be prepared by oxidising a compound of formula(IV)A:

under oxidation conditions described hereinabove. Compounds of formula(IV)A may be prepared according to the general procedures of Scheme 1 byemploying sulfonyl derivatives in place of the corresponding sulfidecompounds of formulae (VI) and (VII).

It will be appreciated by those skilled in the art that compounds offormula (I) may be prepared by interconversion, utilising othercompounds of formula (I) as precursors. Suitable interconversions, suchas alkylations, are well known to those skilled in the art and aredescribed in many standard organic chemistry texts, such as ‘AdvancedOrganic Chemistry’ by Jerry March, fourth edition (Wiley, 1992),incorporated herein by reference. For example, compounds of formula (I)wherein R¹ or R² is C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₆alkynyl,C₃₋₁₀cycloalkylC₀₋₆alkyl or C₄₋₁₂bridged cycloalkane may be prepared byalkylating the corresponding compound of formula (I) wherein R¹ is H.

Acylation of compounds of formula (I) wherein R³ is NH₂, to providecompounds of formula (I) wherein R³ is NHCOR⁵, may be carried out byconventional means, for example by employing conventional acylatingagents such as those described in ‘Advanced Organic Chemistry’, pp417–424, incorporated herein by reference.

As will be appreciated by those skilled in the art it may be necessaryor desirable at any stage in the synthesis of compounds of formula (I)to protect one or more sensitive groups in the molecule so as to preventundesirable side reactions. The protecting groups used in thepreparation of compounds of formula (I) may be used in conventionalmanner. See, for example, those described in ‘Protective Groups inOrganic Synthesis’ by Theodora W Green and Peter G M Wuts, secondedition, (John Wiley and Sons, 1991), incorporated herein by reference,which also describes methods for the removal of such groups.

Amines of formula (II) are either known compounds or may be prepared byliterature methods, such as those described in ‘Comprehensive OrganicTransformations: a guide to functional group preparations’ by RichardLarock (VCH, 1989), incorporated herein by reference.

Thioronium salts of formula (V) are either known compounds or may beprepared by literature methods, such as those described in A H Owens etal, Eur J Med Chem, 1988, 23(3), 295–300, incorporated herein byreference

Acetophenones of formula (VII) are either known compounds or may beprepared by conventional chemistry.

Certain intermediates described above are novel compounds, and it is tobe understood that all novel intermediates herein form further aspectsof the present invention. Compounds of formulae (III) and (IV) are keyintermediates and represent a particular aspect of the presentinvention.

Conveniently, compounds of the invention are isolated following work-upin the form of the free base. Pharmaceutically acceptable acid additionsalts of the compounds of the invention may be prepared usingconventional means.

Solvates (e.g. hydrates) of a compound of the invention may be formedduring the work-up procedure of one of the aforementioned process steps.

The Examples that follow illustrate the invention but do not limit theinvention in any way.

EXAMPLE 1N-Butyl-4-(fluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine

LC/MS: retention time 3.38 min; MH+338.3

N-butyl-4-(fluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine

EXAMPLE 2N-butyl-4-(difluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine

Example 2 was prepared in an analogous fashion to Example 1 above,replacing ethyl fluoroacetate with ethyl difluoroacetate in the firststage of the reaction sequence.

LC/MS: retention time 3.48 min; MH+356

Biological Data

Microsomal Assay

Inhibitory activity against microsomal h-COX2 was assessed against amicrosomal preparation from baculovirus infected SF9 cells. An aliquotof microsomal preparation was thawed slowly on ice and a 1/40,000dilution prepared from it into the assay buffer (sterile water, degassedwith argon containing 100 mM HEPES (pH 7.4), 10 mM EDTA (pH7.4), 1 mMphenol, 1 mM reduced glutathione, 20 mg/ml gelatin and 0.001 mMHematin). Once diluted the enzyme solution was then sonicated for 5seconds (Branson sonicator, setting 4, 1 cm tip) to ensure a homogeneoussuspension. 155 μl enzyme solution was then added to each well of a96-well microtitre plate containing either 5 μl test compound (40×required test concentration) or 5 μl DMSO for controls. Plates were thenmixed and incubated at room temperature for 1 hour. Following theincubation period, 40 μl of 0.5 μM arachidonic acid was added to eachwell to give a final concentration of 0.1 μM. Plates were then mixed andincubated for exactly 10 minutes (room temperature) prior to addition of25 μl 1M HCl (hydrochloric acid) to each well to stop the reaction. 25μl of 1M NaOH (sodium hydroxide) was then added to each well toneutralise the solution prior to determination of PGE₂ levels by enzymeimmunoassay (EIA).

The following IC₅₀ values for inhibition of COX-2 and COX-1 wereobtained from the microsomal assay for compounds of the invention:

Example No. COX-2: IC₅₀ (nM) COX-1: IC₅₀ (nM) 1 761 >10,000 2 17 >94,000

1. A compound of formula (I)

or a pharmaceutically acceptable salt thereof, in which: R¹ and R² areindependently selected from the group consisting of H, C₁₋₆alkyl,C₂₋₆alkenyl, C₃₋₆alkynyl, C₃₋₁₀cycloalkylC₀₋₆alkyl and C₄₋₁₂bridgedcycloalkyl; R₃ is selected from the group consisting of C₁₋₆alkyl, NH₂and R⁵CONH; R⁴ is selected from the group consisting of CH₂F, CHF₂,CF₃CH₂, CF₃CHF and CF₃CF₂; and R⁵ is selected from the group consistingof H, C₁₋₆alkyl, C₁₋₆alkoxy, C₁₋₆alkylOC₁₋₆alkyl, phenyl, HO₂CC₁₋₆alkyl,C₁₋₆alkylOCOC₁₋₆alkyl, C₁₋₆alkylOCO, H₂NC₁₋₆alkyl,C₁₋₆alkylOCONHC₁₋₆alkyl and C₁₋₆alkylCONHC₁₋₆alkyl.
 2. The compound asclaimed in claim 1 wherein R¹ is H.
 3. A compound as claimed in claim 1,wherein R² is C₁₋₆alkyl.
 4. A compound as claimed in claim 1 wherein R³is C₁₋₆alkyl.
 5. A compound as claimed in claim 1 wherein R⁴ is CH₂F orCHF₂.
 6. A compound as claimed in claim 1 wherein R⁵ is selected fromthe group consisting of C₁₋₆alkyl, phenyl and aminomethyl.
 7. A compoundas claimed in claim 1 wherein R² is straight chain C₁₋₆alkyl or branchedchain C₃₋₆alkyl.
 8. A compound selected from:N-butyl-4-(fluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine;N-butyl-4-(difluoromethyl)-6-[4-(methylsulfonyl)phenyl]pyrimidin-2-amine;and pharmaceutically acceptable salts thereof.
 9. A process for thepreparation of a compound as defined in claim 1, which comprises: (A),reacting an amine HNR¹R² of formula (II) or a protected derivativethereof with a compound of formula (III)

and thereafter and if necessary, (B), interconverting a compound offormula (I) into another compound of formula (I); and/or (C),deprotecting a protected derivative of compound of formula (I).
 10. Apharmaceutical composition comprising a compound as defined in claim 1in admixture with one or more physiologically acceptable carriers orexcipients.
 11. A method of treating a subject suffering from acute orchronic pain which comprises administering to said subject an effectiveamount of a compound as claimed in claim
 1. 12. The method according toclaim 11 wherein said acute or chronic pain is lower back or neck pain.13. The method according to claim 11 wherein said acute or chronic painis neuropathic pain.
 14. The method according to claim 11 wherein saidacute or chronic pain is non-specific lower back pain.
 15. The methodaccording to claim 11 wherein said acute or chronic pain ispost-herpetic neuralgia.
 16. The method according to claim 11, whereinsaid subject is a human.
 17. A method of treating a subject sufferingfrom dysmenorrhoea which comprises administering to said subject aneffective amount of a compound as claimed in claim
 1. 18. The methodaccording to claim 17, wherein said subject is a human.
 19. A method oftreating a subject suffering from arthritis which comprisesadministering to said subject an effective amount of a compound asdefined in claim
 1. 20. The method according to claim 19 wherein saidarthritis is rheumatoid arthritis.
 21. The method according to claim 19wherein said subject is a human.
 22. A method of treating a subjectsuffering from osteoarthritis which comprises administering to saidsubject an effective amount of a compound as defined in claim
 1. 23. Themethod according to claim 22 wherein said subject is a human.